The present invention relates to a drilling system and method for use in gas and oil wells. During the drilling process various types of information are transmitted, by a telemetry system, from one or more sensors that may be proximate to a drilling bit and towards receivers that may be located within a drilling pipe and even on the surface.
The various types of information that should be transmitted by the telemetry system may include bit location, bit orientation, pressure and temperature of the borehole and characteristics of the geological formations.
In some drilling systems the telemetry system is located above a drilling motor, at about 15-30 meters behind the bit, depending on the Bottom Hole Assembly (BHA) composition.
The common methods of powering the telemetry systems in the drilling applications are: (a) primary battery such as, lithium cells or alkaline cells, or (B) using an electrical generator that uses the drilling fluid to provide the force to turn the turbine.
Both of the methods have significant drawbacks. The primary batteries are expensive and hazardous. The disposal of these batteries is a major concern, both in economic sense and because of the impact on the environment by the toxic waste.
The electrical generator often fails due the friction of the moving parts, and does not provide as much power as battery can, especially in small diameter drilling applications.
Also, in some drilling situations (under-balanced drilling) it is not even possible to use the generator. Using a generator can be difficult and even impractical during tripping in the borehole or out of the borehole.